On 12/09, Paul E. McKenney wrote: > > This commit therefore adds a smp_mb__after_unlock_lock(), which may be > placed after a LOCK primitive to restore the full-memory-barrier semantic. > All definitions are currently no-ops, but will be upgraded for some > architectures when queued locks arrive. I am wondering, perhaps smp_mb__after_unlock() makes more sense? Note that it already has the potential user: --- x/kernel/sched/wait.c +++ x/kernel/sched/wait.c @@ -176,8 +176,9 @@ prepare_to_wait(wait_queue_head_t *q, wa spin_lock_irqsave(&q->lock, flags); if (list_empty(&wait->task_list)) __add_wait_queue(q, wait); - set_current_state(state); + __set_current_state(state); spin_unlock_irqrestore(&q->lock, flags); + smp_mb__after_unlock(); } EXPORT_SYMBOL(prepare_to_wait); @@ -190,8 +191,9 @@ prepare_to_wait_exclusive(wait_queue_hea spin_lock_irqsave(&q->lock, flags); if (list_empty(&wait->task_list)) __add_wait_queue_tail(q, wait); - set_current_state(state); + __set_current_state(state); spin_unlock_irqrestore(&q->lock, flags); + smp_mb__after_unlock(); } EXPORT_SYMBOL(prepare_to_wait_exclusive); Assuming it can also be used "later", after another LOCK, like in your example in 5/7. Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
